The process was divided into 4 stages. The first two were handled by the recruitment company and the following two by Coinbase:

1. A recruiter from a specialized recruitment company approached me, and we had a chat to understand if my profile matched what was expected for the position.
2. A programming challenge that involved developing some endpoints and tests, and fixing other tests that were failing.
3. Develop an "iterable" interface and implement this interface for several concrete types: list interaction, range iteration, odd number iteration.
4. Architecture design: outlining how I would implement a messaging system similar to Slack, with endpoints, data modeling, indexes, etc.

What type of database would you use and why?

What query would you make to retrieve all messages in a channel and what indexes would you create on that table?